Imaging systems of the type under discussion such as, for example, medical imaging systems used to provide images for medical diagnostics, generally acquire data, process the data and use the processed data to provide an image or images on a video screen using raster display methods.
The versatility of the system in providing the display image is important for diagnostic purposes. For example, almost all systems now provide "multi-images", that is, more than one image at a time, simultaneously on the video screen. This type of multi-image display is often referred to as a "split screen operation". The images may be of different sections of the body, for example, or different sized images of the same section, or views of the same sections at different times. Part of the screen may be used to display a report (diagrams, text etc.) related to the other images shown on other parts of the screen.
Many functions are performed and many operations may be done in the processing system, in the memory and in the display control system, on the images. Images are zoomed, miniaturized, displayed in cine modes, subtracted in portions, etc. The presently available imaging methods and systems lack versatility when it comes to displaying a relatively large number of images (more than 4) on a video screen. Thus, while many systems do, at the present time, provide "split-screen" operation, these are very limited and rather inflexible.
In the prior art systems, the split screen facility is generally based on either one of the following techniques:
(a) The combination of images to be displayed is stored, under software control, in the display memory. The location, size and other display parameters for each of the images is taken into account during the processing and the thus "edited" image is placed in a corresponding portion of the display memory. The hardware used for display is required only to display the completely edited image and no hardware controls concerned with split screen are used nor required.
(b) Hardware means are built into the display system which support a fixed subdivision of the screen area (i.e one fourth). An attribute control parameter is associated with each of the subdisplays. Thus, some selective control of the subdisplay parameters is available; such as pointer to image address, and priority of display (image, overlay and alphanumerics).
The above prior art techniques are characterized by severe limitations. While the software based system of method (a) is extremely flexible in all display parameters, it requires extensive software processing whenever some change in layout or other display parameter is required. Hence, the response time is normally inadequate for interactive systems. This above described software method also requires larger memory capacity as both the original images and the "edited" images have to be stored in memory, thus duplicating the size of the memory.
The hardware based split screen system (method b) described above) is characterized by a complimentary set of characteristics. In other words, for example, its response time is practically instantaneous, making it suitable for interactive operation ("interactive operation" is defined herein as the capability of the imaging system to vary the images responsive to instructions from the system operator on a real time basis) but it is practically devoid of versatility.
It would be highly desirable to increase the versatility of the split screen operations to the point where all the advantages of both prior art methods described above are realized without their shortcomings, i.e.:
The split screen may be partitioned into a large number of subdisplays;
The subdivisions of the screen are readily and speedily variable; hence, the number of images, their shape/boundaries and the position of the images may be instantaneously changed in the course of an interactive viewing of the images;
Once the screen is partitioned, each subdisplay has an independant set of display parameters; such as, address pointer, zoom factor, interpolation enable, scroll, windowing, etc;
The display parameters are available dynamically at video rates; thus, as long as hardware is available for performing any of the image processing steps at the video rate, this processing step may be applied to those of the subdisplays being refreshed at every given instance as the electron beam scans the display during the refresh cycle.
Accordingly, it is an object of the invention to provide extremely versatile and flexible split screen capability in digital display systems.
According to a broad aspect of the present invention, an imaging display system is provided. The system uses video display means providing split screen features, said system comprising:
display memory means for storing data used to construct the images displayed,
designation means for designating portions of the display area of the video display means as subdisplay areas. Control means for reading out designated images for display, and associate means for changing contents of the designation means, thereby changing the subdisplay area.
According to a feature of the invention, means are provided for storing the display parameters for each subdisplay together with loading means as required to load the storing means with new sets of parameters, and means for dynamically reading out the parameters for controlling the subdisplay being refreshed.
A further feature of the invention includes means for controlling the operation of the system consistent with the overall specification of the display and its split screen.
According to yet another feature of the invention, data transferring means for use in transferring data from the display memory into the display means are provided. This data transferring means includes the designation means for designating portions of the display area of the video display means as subdisplay areas and directing means for directing data from the memory into a specified subdisplay area from any portion of the memory.
The data transferring means comprises dedicated hardware having a subdisplay map including auxiliary memory means plus control hardware to move the pointers on the original memory as directed by the subdisplay map information. In addition, the control hardware determines or is used in selecting the functions to be performed in the subdisplay, such as zooming, cine, etc.